In a digital video broadcasting (DVB) setting, a client device receives a digital broadcast of video and other data from a server device across a broadcast network. A client device may also be called a broadcast receiver, a set-top box, and the like. The server device may also be called a broadcaster or content distributor.
DVB standards and other digital video compression/transmission schemes (such as MPEG-2) include a protocol for broadcasting rotational sequences of data modules, which may be called “carousels.” An example of one such protocol is DSMCC (Digital Storage Media Command and Control).
Broadcasting Carousels
A carousel is a mechanism for delivering blocks of data over a one-way (e.g., broadcast) network. The blocks of data are called modules. These modules are repeatedly rebroadcast over and over again. Hence, the term “carousel.” A carousel may also be called a rotational sequence of modules.
Primarily, DSMCC is a protocol for controlling a video-on-demand (VOD) server and providing data and object carousels. It designed for receivers (e.g., clients) to fetch select data received from a sender (e.g., server).
Clients are, in general, devices such as set top boxes that consume multi-media content. Servers are entities that provide multi-media content and services. A Server may be a distributed system and contain multiple computing platforms, some functionally specialized e.g. video pumps to provide video-on-demand service.
The DSMCC carousel protocol makes use of non-flow-controlled download messages to provide periodic broadcast of data to a set of receivers. A download control message provides a list of available modules from a particular data carousel so that each receiver can identify which modules it wishes to capture. Since for the data carousel case, no reverse channel from receiver to sender is present, it is assumed that all data transfer parameters have been agreed upon a priori, and that the receiver knows on which broadcast channel to start listening for download control and data messages.
Object carousels, specifically, are a more structured form of the DSMCC data carousels. The content of the modules of an object carousel are identified to the broadcast receiver. Examples of identified objects include files, directory, images, sound, etc.
DSMCC carousels are well-known to those of ordinary skill in the art.
Broadcast Communications
Typically, communications networks may be classified as either one-way or two-way. With a one-way network, communication occurs only in one direction: From the source to the receiver with no return channel of communications (or a limited one). With a two-way network, communication occurs freely in both directions, more or less, without limitation.
A one-way network is often called a “broadcast” network. A broadcast network is one that primarily “broadcasts” (e.g., transmits) information to consumers of that signal. A satellite network is an example of a typical broadcast network. A conventional cable network is one-way; however, some are two-way. Typically, DVB is over a broadcast network. A ubiquitous example of a two-way network is the Internet. Also, local area networking (LAN) and wide area networking (WAN) are other examples.
Interactivity
With two-way communications, it is possible for the nodes (e.g., server or client) on either end of the communications network to interact with each other. Being interactive may be that which relates to a two-way electronic or communications system in which response is relatively direct and continual.
It is rather straightforward to implement interactivity via a two-way network. Browsing the web involves interactivity between the user of the web browser and the web servers.
However, true interactivity between two nodes on the network is not possible on a true one-way network. Even if it is possible via a slow or delayed backchannel, true interactivity is not practical because the delay of the backchannel does not provide a mechanism for relatively direct and continual responses between nodes.
Accordingly, it is a challenge to provide internet-like (e.g., hypertext or web) interactivity for users of client devices over a broadcast communications network.